Remove empty lines from string, but allow one empty between every line

Question

I would like to remove excessive empty lines from a string, but allow one empty line between every line. Like:

line1





line2

Should become:

line1

line2

I did find the following regex (forgot where i found it):

preg_replace('/^\n+|^[\t\s]*\n+/m','',$message);

This works, but removes all empty lines without leaving an empty line between every line.

Edit: I just created a quick example at http://jsfiddle.net/RAqSS/

Basically if there are more than 2 empty lines between every line, it should be trimmed down to just one. So basically that remaining empty line should be as high as 1 em. — Sempiterna
– Sempiterna, Commented May 18, 2012 at 16:01
I think you need to define what you mean by 'empty line'. What you describe in the question isn't an empty line. — Kendall Frey
– Kendall Frey, Commented May 18, 2012 at 16:10

Kendall Frey · Accepted Answer · 2012-05-18 16:20:53Z

7

Try replacing:

\n(\s*\n){2,}

with:

\n\n

Like this:

preg_replace('/\n(\s*\n){2,}/', "\n\n", $message); // Quotes are important here.

If you don't want an empty line, you would change the {2,} to a + and use a single \n. It would actually work with a + instead of {2,}. The {2,} is an optimization.

edited May 18, 2012 at 16:20

answered May 18, 2012 at 16:01

Kendall Frey

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1 Comment

Devner Over a year ago

This one works precisely! If you don't want empty line, you would use the following code: preg_replace('/\n(\s*\n)+/', "\n", $output);

Andrew Clark · Accepted Answer · 2012-05-18 16:27:40Z

4

Try the following:

preg_replace('/\n(\s*\n)+/', "\n\n", $message);

This will replace a newline followed by any number of blank lines with a single newline.

edited May 18, 2012 at 16:27

answered May 18, 2012 at 16:00

Andrew Clark

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8 Comments

Sempiterna Over a year ago

That doesn't work. It somehow removes all content, leaving an empty string.

Kendall Frey Over a year ago

'\n' is not a single newline.

Andrew Clark Over a year ago

@KendallFrey - Thanks, originally OP was asking for line\nline2 but it looks like you were interpreting it correctly based on the jsfiddle.

Andrew Clark Over a year ago

@Sempiterna - I just noticed that I had forgotten the trailing / on the regex, that may have caused the problem. Glad you were able to find a working solution!

Kendall Frey Over a year ago

By the way, see mine and AshleyS's answers for the correct way to put a newline in string.

|

sudoash · Accepted Answer · 2012-05-18 16:29:27Z

0

Based on your jsFiddle, try this:

$result = preg_replace('/\n(\n*\s)+/', "\n\n", $message);

edited May 18, 2012 at 16:29

answered May 18, 2012 at 16:07

sudoash

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2 Comments

Sempiterna Over a year ago

Your second code almost works. It replaces all empty lines and replaces them with an empty line between each piece of text. But it also adds an empty line between each piece of text that did not have multiple empty lines.

sudoash Over a year ago

Can you update your question with a more detailed example of your data and expected results?

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